OBJECTIVETo study the changes in activity of phosphatidylinositol 4 kinase (PI 4 kinase), phosphatidylinositol 4 phosphate 5 kinase (PIP 5 kinase) and protein kinase C (PKC) during myocardial ischemia and elucidate the relationship between phosphatidylinositol signal pathways and prolonged myocardial ischemia.

METHODSIn vivo an ischemic rat model was used. Activity of PI 4 kinase, PIP 5 kinase and PKC were measured at different times in postischemic heart cells using isotope analysis.

RESULTSThe activity of PI kinase, PIP kinase and PKC in the myocardium increased to peak at 1 hour postischemia, with activities 6.1, 3.0 and 4.0 fold over control levels, respectively. Their activities declined to normal levels with time.

CONCLUSIONThe phosphatidylinositol signal pathway is involved in prolonged myocardial ischemia, but its mechanism needs further study.

1-Phosphatidylinositol 4-Kinase ; metabolism ; Animals ; Male ; Myocardial Ischemia ; enzymology ; Phosphotransferases (Alcohol Group Acceptor) ; metabolism ; Protein Kinase C ; metabolism ; Random Allocation ; Rats ; Rats, Wistar ; Signal Transduction

OBJECTIVETo construct a phosphatidylinositol 4-kinase beta (PI4K-beta) mutant with the 325th to 373rd amino acid codons deleted, and try to develop a simple method for constructing middle fragment deletion mutant.

METHODSIn line with the mechanism of gene splicing by overlap extension(SOE), an additional PCR was used to get the PI4K-beta mutant in which the 325th to 373rd amino acid codons were deleted. Then the mutated gene was cloned into pCMV-Tag4A mammalian expression vector.

RESULTSA mutant with the 325th to 373rd amino acid codons deleted was constructed successfully.

CONCLUSIONThe improved SOE is a very effective and reliable method to construct middle fragment deletion mutant. It is worthy to be popularized.

1-Phosphatidylinositol 4-Kinase ; genetics ; Base Sequence ; Genetic Vectors ; genetics ; Molecular Sequence Data ; Mutagenesis, Site-Directed ; Mutation ; genetics ; Polymerase Chain Reaction ; methods ; Protein Engineering ; methods ; Recombinant Proteins ; genetics ; Sequence Deletion

PURPOSE: PTEN/MMAC1, a novel tumor suppressor gene, is mutated in a variety of advanced and metastatic cancers. It acts as a phosphatase, and thereby, regulates the PI-3 kinase/Akt pathway. In this study, we examined to evaluate the new function of anti-tumor effects of PTEN/MMAC1 through the regulation of the IGFs-IGFBPs in gastric cancer cells. METHODS: PTEN/MMAC1 was expressed in an adenovirus-mediated gene delivery system and introduced into gastric cancer cells(SNU-484 & SNU-668) in vitro. The effect of cell growth and the expression of IGFs and IGFBPs after Ad/PTEN infection was analyzed by MTT assay, RT-PCR and Western immunoblot. RESULTS: Ad/PTEN infected cells were inhibited in cell growth compared with moak cells and Ad/ LacZ infected cells. Overexpression of PTEN/MMAC1 induced decrease in expression of IGF-I, -II and IGF-I receptors which are known as growth prompt molecules in a variety of cancers. Of the six IGFBPs, the expressions of IGFBP-4 and IGFBP-6 were decreased in Ad/PTEN infected cells. In contrast, IGFBP-3 expression was markedly increased by up to 3-fold in Ad/PTEN infected cells. Overexpression of PTEN/MMAC1 inhibited the activation of Akt/PKB pathway, but had no effect on the MAPK pathway. CONCLUSION: These findings suggest that the tumor suppressor function of PTEN/MMAC1 is, at least in part, mediated through the down-regulation of IGF-I abd IGF-II, and up-regulation of IGFBP-3 in gastric cancer cells by the inhibition of PI-3 kinase pathway.
Blotting, Western ; Down-Regulation ; Gene Transfer Techniques ; Genes, Tumor Suppressor ; Insulin-Like Growth Factor Binding Protein 3 ; Insulin-Like Growth Factor Binding Protein 4 ; Insulin-Like Growth Factor Binding Protein 6 ; Insulin-Like Growth Factor Binding Proteins* ; Insulin-Like Growth Factor I ; Insulin-Like Growth Factor II ; Phosphatidylinositol 3-Kinase ; Phosphatidylinositol 3-Kinases ; Receptor, IGF Type 1 ; Stomach Neoplasms ; Up-Regulation